In a gas-insulated switchgear, a center conductor to which a high voltage is applied is accommodated in a metallic grounded tank, and insulation gas is confined to a space between the grounded tank and the center conductor, so that insulating performance is ensured. However, during manufacture or installation to a site, a foreign substance (dust, fiber, conductive or nonconductive solid substance, or the like) may be mixed into the grounded tank and deteriorates the insulation performance. The mixed foreign substance becomes charged by an electric field generated during current application, and receives an electrostatic force in an upward floating direction from the inner surface of the grounded tank. When the electrostatic force exceeds the gravity force acting on the foreign substance, the foreign substance floats up and moves toward the center conductor. When the foreign substance approaches or adheres to the center conductor, the electric field becomes locally high because the electric field is concentrated around the foreign substance. This may deteriorate the withstand voltage performance of the switchgear. In particular, when the foreign substance is metallic and linear, the insulation performance is considerably deteriorated because the electric field is intensely concentrated at an end of the foreign substance.
To address the problem about the metallic foreign substance, for example, in a conventional gas-insulated switchgear disclosed in Patent Document 1, a nonlinear resistive film having nonlinear resistance characteristics is provided on the tank inner surface thereof, thereby suppressing partial discharge around a metallic foreign substance and preventing the metallic foreign substance from becoming charged. Thus, floatation of the metallic foreign substance is suppressed.